1. Field of the Invention
The present invention relates to a technique for preventing a rear-end collision between vehicles such as automobiles, which move independently of each other. In particular, the invention relates to rear-end collision alarming device and method, in which a distance from a subject vehicle to a preceding vehicle is measured, and the measured distance is utilized for preventing a rear-end collision of the subject vehicle against the preceding vehicle.
2. Description of the Background Art
Vehicles such as automobiles move on roads independently of each other. Therefore, there is a possibility of an accident such as a contact between vehicles. Particularly on expressways or the like, rear-end collisions happen frequently, and result in serious situations due to high running speeds of vehicles.
A major cause of the rear-end collision is an excessively short distance between automobiles. Accordingly, various devices for preventing the collision have been proposed. The device in the prior art generally includes a distance measuring device which is mounted on a vehicle for measuring a distance, a relative speed or the like between the subject and preceding vehicles, and determines the possibility of rear-end collision based on the detected distance, relative speed or the like.
When the distance between the subject and preceding vehicles decreases, a driver generally releases a gas pedal and/or depresses a brake pedal to decrease a running speed and increase the following distance to the vehicle in front. When the distance increases to a safe value, the driver increases the speed to a former proper value. In this manner, each driver operates the vehicle properly in accordance with a variation in distance between the subject and preceding vehicles so that a rear-end collision can be prevented, and safe driving of a plurality of vehicles is ensured.
Accordingly, one of major causes of the rear-end collision is that drivers did not properly perform a series of foregoing operations. Thus, the rear-end collision occurs when a driver does not perform a series of foregoing operations at all, or perform the operations with proper timing. More specifically, the collision occurs when a driver looked aside or fell asleep.
However, such a device has not yet become widely available that can accurately detect the possible facts that a series of necessary operations is not performed at all or performed with a delay due to looking-aside or a doze during driving, and can reliably prevent the rear-end collision. It is preferable to prevent the rear-end collision without requiring a driver's operation, but it is also desirable to notify a driver of a possibility of the rear-end collision for requesting an appropriate operation by the driver.
Accordingly, an object of the invention is to provide a rear-end collision alarming device which issues to a driver in a subject vehicle an alarm relating to a following distance to a vehicle in front, and/or applies forcedly a brake in some cases for preventing the rear-end collision, when the subject vehicle approaches the preceding vehicle and the driver does not react on it to keep a safe distance, as well as a method of displaying the following distance.
Another object of the invention is to provide a rear-end collision alarming device which determines whether a driver in a subject vehicle does a series of operations to be performed or not when the subject vehicle approaches the preceding vehicle, and can issue an alarm for preventing a rear-end collision, and/or can apply forcedly a brake in some cases for preventing the rear-end collision as well as a method of displaying the following distance.